Significant Accounting Policies (Details 4) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Noncontrolling interests:
Balance			$ 5,951,505
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized gain (loss) on derivative hedge agreements	$ 9,240	$ (8)	19,339	$ (7,541)
Net (gain) loss reclassified from accumulated other comprehensive loss into earnings	(77,536)	2,577	(74,909)	5,274
Currency translation adjustments	(14,282)	4,046	(138,793)	17,779
Changes in available-for-sale securities and other	(27,721)	202	(22,084)	682
Purchase and dispositions of noncontrolling interests, net and other			3,278
Balance	5,179,149		5,179,149
Noncontrolling Interests
Noncontrolling interests:
Balance	828,618	989,988	858,328	973,226
Net income attributable to noncontrolling interests after preferred distributions and income attributable to redeemable noncontrolling interests in consolidated properties	80,269	70,060	142,290	127,710
Distributions to noncontrolling interest holders	(78,488)	(74,029)	(153,398)	(151,465)
Other comprehensive income (loss) allocable to noncontrolling interests:
Unrealized gain (loss) on derivative hedge agreements	1,380	(17)	2,861	(1,253)
Net (gain) loss reclassified from accumulated other comprehensive loss into earnings	(11,126)	376	(10,745)	768
Currency translation adjustments	(1,667)	586	(19,665)	2,518
Changes in available-for-sale securities and other	(4,141)	30	(3,364)	102
Other comprehensive income (loss)	(15,554)	975	(30,913)	2,135
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	(75,905)	(121,454)	(81,529)	(188,680)
Units issued to limited partners				84,910
Exchange of limited partner units for common shares	(56)	(279)	(7,905)	(1,190)
Units Redeemed	(14,843)		(14,843)
Long-term incentive performance units	11,812	12,484	23,640	24,969
Purchase and dispositions of noncontrolling interests, net and other	415	4,599	598	10,729
Balance	$ 736,268	$ 882,344	$ 736,268	$ 882,344